Field of the Invention
The present invention is in the technical field of civil engineering and is directed generally toward methods and devices for supporting excavations.
Description of the Related Art
The boundary of an excavated space may include one or more substantially vertical sidewalls cut into the soil. One or more temporary support structures, such as contiguous temporary support-of-excavation (“SOE”) walls, are typically installed to support the sidewalls cut into the soil and prevent these sidewalls from collapsing into the excavated space. Examples of contiguous temporary SOE walls include but are not limited to diaphragm walls, cutter-soil-mix slurry walls, and secant pile walls.
A contiguous temporary SOE wall is typically anchored to the soil behind the wall by tieback anchors. Tieback anchors, which are considered active restraint devices, typically include steel cable strands that extend from the wall into the soil, and are grouted into the soil behind the wall. After being grouted into the soil, the tieback anchors are tensioned to a high load using a hydraulic jack. Tieback anchors tensioned in this manner are referred to as being “active.”
Unfortunately, conventional methods of attaching tieback anchors to a contiguous temporary SOE wall suffer from several shortcomings. For example, conventional methods of attaching tieback anchors to a contiguous temporary SOE wall are labor-intensive. Further, tieback anchors installed using conventional methods typically intrude into the excavated space.
A contiguous temporary SOE wall is needed only until a permanent structure (e.g., permanent concrete walls) designed to support the sidewalls of the excavated space is placed or constructed in front of the contiguous temporary SOE wall. After the permanent structure is in place, active tieback anchors are generally considered a liability. Accidentally cutting an active tieback anchor has the potential to cause bodily harm to workers, damage to the permanent structure, or damage to excavation equipment. As a result, most government authorities having jurisdiction over an excavation require that the tension in the tieback anchors be released (referred to as “de-tensioning”) before project completion such that future construction activities will not accidently cut through and inadvertently de-tension one or more of the active tieback anchors.
Unfortunately, no simple means exists for de-tensioning conventional tieback anchors after the permanent structure has been placed or constructed in front of the contiguous temporary SOE wall. In order to facilitate de-tensioning of the tieback anchors, windows or voids are typically incorporated into the permanent structure at locations adjacent to the tieback anchors. These voids provide temporary access to permit removal or de-tensioning of the tieback anchors. Before commissioning the permanent structure, these voids must be filled with concrete. Filling these voids and repairing any associated waterproofing penetrations is time-consuming and expensive, and may compromise the integrity of the permanent structure.
Therefore, a need exists for new methods and devices for attaching tieback anchors to a contiguous temporary SOE wall. Methods and devices that allow active tieback anchors to be more easily de-tensioned are particularly desirable. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.